Urinary incontinence is a prevalent condition with significant social, economic, quality of life, and medical consequences. The reported prevalence has been variable depending upon the manner in which the problem has been defined. When referring to incontinence of any degree, an overall prevalence of 29 percent of women has been reported. Incontinence of severe degree was reported in 7 percent of women. Age is a significant factor with relatively few young women reporting daily leakage, but daily or severe leakage occurs in 10 percent of middle-aged women. Various classification schemes for urinary incontinence have been described, a non-limiting example of which includes the types of incontinence referred to as stress incontinence, urge incontinence, mixed incontinence, overflow incontinence, continuous incontinence, and situational incontinence.
A frequent clinical problem is the type of incontinence referred to as “stress urinary incontinence” or “stress incontinence.” Stress incontinence has been described as the “involuntary leakage of urine on effort or exertion.” It is the most common type of incontinence for which women seek the advice of a clinician. Causes of stress urinary incontinence include urethral hypermobility, intrinsic sphincter deficiency, and combinations thereof.
Urethral hypermobility involves the rotational descent of the bladder neck and proximal urethra during increases in abdominal pressure. Descent of these structures below the pelvic floor allows the disproportionate transfer of abdominal pressure to the bladder relative to the urethra. As the bladder pressure exceeds the urethral closure pressure, leakage ensues. Leakage will typically occur during physical activity such as coughing, sneezing, laughing, lifting, or exercise.
Intrinsic sphincter deficiency (ISD) denotes an intrinsic malfunction of the urethral sphincter, regardless of its position or descent during physical stress. Thus, the urethral closure pressure is inadequate to maintain continence even when the urethra is positioned appropriately. Conditions often associated with an increased risk of ISD include previous urethral or periurethral surgery, neurological problems, radiation, and estrogen deficiency.
Physical therapy has been recommended as a first line approach in the treatment of stress incontinence. When physical therapy has been unsuccessful, various surgical procedures have been employed. In recent decades, surgeons have based their recommendations regarding the most suitable type of surgical procedure on the distinctions between urethral hypermobility and intrinsic sphincter deficiency. It has been common practice to recommend a suspension procedure for the former and a sling or bulking procedure for the latter. More recently this approach has been called into question because many women have contributing components of both disorders.
Suspension techniques commonly used for the treatment of urethral hypermobility include the Marshall-Marchetti-Krantz procedure and the Burch procedure. The Marshall-Marchetti-Krantz (MMK) procedure suspends the bladder by placing sutures at the periosteum of the pubis or pubic symphysis. The Burch procedure achieves support by suturing to Cooper's ligament. Although cure rates of 80 percent have been reported, these procedures traditionally require open surgical exposure and hospitalization for recovery. The laparoscopic Burch procedure offers a minimally invasive approach; however, the effectiveness is less satisfactory.
Suburethral sling procedures also are used to treat incontinence. These procedures provide stabilization of urethral position and/or compression of the urethra by placing a strip of tissue or other material beneath the urethra. The strip of material has sometimes been described as a hammock or backboard. A compressive sling is required when urethral function is very poor. Autologous fascia has been used for this procedure, although xenografts (such as porcine dermis) and synthetic materials also have been used. There are concerns regarding both autologous and xenographic materials, however, with regard to durability. And there is the possibility of severe long-term complications from use of synthetic materials.
Another method of treatment commonly used for treating ISD involves the injection of bulking agents into the periurethral tissue. Various injectable substances have been used, including polytetrafluoroethylene (PTFE), collagen, silicone, and carbon coated beads; however, an ideal material has yet to be developed. Bovine collagen, generally recognized as the most widely used agent, has had disappointing long-term effectiveness, while use of PTFE has raised concerns about the unintended migration of non-degradable implanted particles to other parts of the body.
More recently, the TVT (Tension-free Vaginal Tape) procedure has become a popular treatment for stress incontinence. TVT procedures involve the implantation of a proprietary polypropylene mesh tape at the mid-urethral level. The simplicity of the implantation procedure allows the procedure to be done in a relatively short period of time on an outpatient basis. Although the initial reports indicate low rates of complications, recent reports indicate that complications with the TVT procedure have been significantly underreported. Notably, passage of the instruments and sling material through the retropubic space in close proximity to important anatomical structures is performed without visualization during the procedure, sometimes resulting in complications such as bladder perforation, major vascular injuries, bowel injury, and nerve entrapment. In addition, there is concern about the potential for developing long-term complications from the permanent and synthetic implant material in this location. Such complications may include urethral erosion, vaginal extrusion, and voiding dysfunction. Although the TVT procedure easily may stabilize a hypermobile urethra, it is important to weigh the convenience of the implantation procedure against both the risks of the procedure and the potential long-term complications that may arise from a permanent implant.
The TOT (trans-obturator tape) procedure recently has gained popularity as an alternative to the TVT procedure. This procedure involves the passage of a propylene mesh tape through the obturator membrane instead of the retropubic space to avoid some of the problems associated with the TVT procedure. There is a scarcity of data, however, regarding the long-term safety or effectiveness of this procedure. In addition, the occurrence of protracted upper leg pain has been reported as a troubling complication in some patients.
Thus, a need remains for improved techniques for treating stress urinary incontinence. It would be particularly desirable to provide methods and devices that are minimally invasive and provide long-term correction or continence improvement, while avoiding the use of permanent (e.g., non-degradable) implant structures.